1. Field of the Invention
The present invention relates to techniques for manipulating digital images. More specifically, the present invention relates to a method and an apparatus for previewing digital motion picture content.
2. Related Art
As computer systems are becoming more powerful, they are increasingly being used for computationally intensive image-processing tasks. Specifically, the motion picture industry is increasingly relying on computer systems to modify and preview films.
FIG. 1 presents a flowchart that illustrates a digital motion picture workflow.
A typical digital motion picture workflow begins when scene 102 is captured on negative film 104 by a camera. Next, the camera's negative film 104 is scanned to produce digital picture file 106. Note that the digital picture file can be encoded in a number of file formats. For example, the digital picture file can be a DPX/Cineon file.
The digital picture file can then be edited on a computer system and recorded onto negative film 110. Next, negative film 110 can be processed to produce positive print film 112. Finally, the positive print film can be shown in a theatre by projecting it on theatre screen 114.
Editing a digital picture file on a computer system can adversely affect the appearance of the edited scenes when they are projected on a theatre (or cinema) screen. Specifically, scenes or special effects that were added or manipulated during the editing process may not match the look and feel of unedited scenes. Hence, it is very important to be able to preview the motion picture as it will appear on the theatre screen so that such discrepancies can be fixed before the film is developed.
Note that digital picture file 106 can be used to generate preview 108 of the digital motion picture as it would appear on the theatre screen 114. Some prior art techniques use a look-up table to convert input pixel values in digital picture file 106 to output pixel values that correspond to what appears on theatre screen 114.
Usually, prior art techniques use empirical techniques to generate the look-up table. A special digital picture file that contains a number of color patches is developed and projected onto a theatre screen. Next, the color of a region in the projected picture is compared with the color of the corresponding region in the digital picture file to determine the value of the corresponding entry in the look-up table.
Unfortunately, these prior art techniques have a number of disadvantages. First, these techniques are time consuming and labor intensive because they require the color patch picture to be developed before the look-up table can be determined. Second, the film development process can produce variable results which can adversely affect the accuracy of the look-up table. Third, the measured values are subject to instrument noise, especially in dark patches, which can also decrease the accuracy of the look-up table. Finally, these prior art techniques are usually not flexible, i.e., if even one of the steps in the motion picture workflow is modified, the whole film development process has to be repeated to generate a new look-up table that captures the effect of the modified workflow.
Hence, what is needed is a method and an apparatus to preview digital picture content on a computer monitor as it would appear projected in a theatre without the above-described drawbacks.